Ignition system and control method
An ignition system is provided. The ignition system includes at least one ignition module, which has an input end to receive control signal from the ECU, and an output end to supply ignition energy to the spark gap. The ignition module provides on-demand ignition energy based on an engine operation conditions with adaptively controlled discharge current amplitude and duration using prompt feedback signals measurement of the plasma impedance.
1 . A method to control an ignition system, comprising following steps:
S1, spark initiation, utilizing a dedicated ignition coil to build up high voltage to establish a plasma channel;
S2, continuous discharge process, supplying a constant discharge current after establishment of the plasma channel; and
S3, plasma diagnostic during a continuous discharge process, dynamically adjusting a discharge current amplitude based on a feedback signal from a plasma impedance to avoid blow-off and restrike of the plasma channel due to an in-cylinder flow, wherein the ignition system comprises:
at least one ignition module, wherein the at least one ignition module comprises:
an input end, configured to receive a command from an electronic control unit; and
an output end, electrically coupled to a spark plug, wherein the output end is configured to deliver spark energy to a spark gap,
wherein the at least one ignition module is configured to supply the spark energy adaptively based on engine operation conditions.
2 . The method of claim 1 , wherein the at least one ignition module comprises a control unit, at least one ignition energy management unit and the dedicated ignition coil, and an output end of the at least one ignition energy management unit is connected in parallel with an output end of the dedicated ignition coil, then connected to the spark plug;
the control unit is configured to receive a feedback signal including a plasma impedance signal and a combustion diagnostic signal to adaptively deliver an on-demand ignition energy according to an engine need via the at least one ignition energy management unit.
3 . The method of claim 1 , wherein the at least one ignition module comprises one ignition energy management unit and multiple dedicated ignition coils, and the number of the dedicated ignition coils equals the number of spark plugs; the output end of each dedicated ignition coil is electrically coupled to each spark plug separately, while an output end of the ignition energy management unit is split and then electrically coupled to all the spark plugs.
4 . The method of claim 2 , wherein the dedicated ignition coil comprises a primary coil and a secondary coil; the primary coil is coupled to an electronic switch to receive an ignition command to charge the dedicated ignition coil, and the secondary coil has an output end coupled to the spark plug.
5 . The method of claim 4 , wherein the output end of the at least one ignition energy management unit and the dedicated ignition coil are electrically coupled to a single directional circuit before coupled to the spark plug.
6 . The method of claim 4 , wherein the dedicated ignition coil is configured to measure a plasma voltage and send a voltage signal to the control unit.
7 . The method of claim 4 , wherein the at least one ignition energy management unit comprises multiple ignition coils connected in parallel; an output end of each ignition coil is electrically coupled to a high voltage diode, and then coupled with each other in parallel to form the output end, which is then split to coupled with spark plugs.
8 . The method of claim 7 , wherein if the number of the ignition coil is n, a discharge duty cycle of each ignition coil is equal to and within a range between 1/n to (n−1)/n, where n is equal to or greater than 3.
9 . The method of claim 7 , wherein a turning ratio of the ignition coil is within a range of 25:1 to 60:1.
10 . The method of claim 4 , wherein the at least one ignition energy management unit comprises a DC-DC converter, an energy storage capacitor, and a high voltage electronic switch, an input side of DC-DC converter is connected to a power source, while an output side of the DC-DC converter is connected to the energy storage capacitor;
one end of the high voltage switch is electrically coupled with an output end of the energy storage capacitor, the other end of the high voltage switch merged with the output end of the dedicated ignition coil, then coupled to the spark plug.
11 . The method of claim 1 , wherein in step S3, a discharge voltage is collected to calculate the plasma impedance as the feedback signal for enhancing the discharge current amplitude when the discharge voltage is above a certain threshold.
12 . The method of claim 11 , wherein in step S3, a speed of the in-cylinder flow is determined based on a changing rate of the plasma impedance; if the speed of the in-cylinder flow is low, using a first control strategy, if the speed of the in-cylinder flow is high, using a second control strategy.
13 . The method of claim 12 , wherein when the first control strategy is used, a discharge event is controlled to have a first discharge power and a first discharge duration.
14 . The method of claim 12 , wherein when the second control strategy is used, a restrike/blow-off tendency is predicted, and the discharge current amplitude is promptly increased if the restrike/blow-off tendency is high.
15 . The method of claim 14 , wherein the second control strategy predicts the restrike/blow-off tendency via a changing rate of the discharge voltage and an amplitude of the discharge voltage.
16 . The method of claim 14 , wherein the second control strategy estimates the speed of the in-cylinder flow based on the changing rate of the discharge voltage.
17 . The method of claim 14 , wherein the second control strategy controls both a discharge current amplitude and a discharge duration based on combustion diagnostic and plasma diagnostic, wherein
if the restrike/blow-off tendency is high but a combustion state is normal, then only increasing the discharge current amplitude;
if the restrike/blow-off tendency is high and partial burn is detected, then increasing the discharge current amplitude and prolonging the discharge duration;
if the restrike/blow-off tendency is low but the partial burn is detected, then only prolonging the discharge duration.
18 . The method of claim 17 , wherein the combustion diagnostic provides voltage pulses via an ignition energy management unit after a spark event to initiate the plasma channel using a voltage lower than a breakdown voltage threshold, wherein
if the discharge voltage/current is detected, the combustion state is considered normal;
if the discharge voltage/current is not detected, the combustion state is considered as the partial burn.
19 . The method of claim 17 , wherein the combustion diagnostic determines a combustion state based on the plasma impedance after the spark event.
20 . The method of claim 17 , wherein the combustion diagnostic determines a combustion state based on a changing slope of the plasma impedance under a specific discharge current amplitude, wherein
if the changing slope is lower than a reference slope under an air condition, the combustion state is considered normal;
if the changing slope is the same or higher than the reference slope under the air condition, the combustion state is considered as the partial burn or misfire.